Your comment about spacing off the core is interesting: my Drake AMU has an
attached balun which is constructed with the wire wound on a former which
stands the turns off the core. The wire is 1mm diameter bare wire and does
not touch at any point. I have never seen this anywhere else. The core is
also bare, ie no visible coating. I do not know its material.
David
G3UNA
----- Original Message -----
From: "Jack Smith" <[EMAIL PROTECTED]>
To: "Ron D'Eau Claire" <[EMAIL PROTECTED]>
Cc: <[email protected]>
Sent: Monday, February 26, 2007 6:17 PM
Subject: Re: [Elecraft] Toroids - Effect of Winding Spacing on
InductanceandDistributed Capacitance
As far as cores being non-conductive, that is true for powdered iron (the
typical red and yellow cores) but it is not necessarily true for ferrite
cores. The bulk resistivity of ferrite materials varies widely from 1E9
down to 50 ohm-cm, and not all (few, actually in my limited experience)
ferrite cores are coated with a insulating surface. In addition, many
ferrite materials have an extremely high dielectric constant, which
suggests the need for a bit of spacing between the core and the winding to
reduce distributed capacitance arising from paths through the core
(obviously more important when the core is more
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